Deprecate NonThreadSafe in storage/browser/blob in favor of SequenceChecker.

Note to crash team: This CL is a refactor and has no intended behavior change.

This change was scripted by https://crbug.com/676387#c8.

Note-worthy for the reviewer:
 * SequenceChecker enforces thread-safety but not thread-affinity!
   If the classes that were updated are thread-affine (use thread local
   storage or a third-party API that does) they should be migrated to
   ThreadChecker instead.
 * ~NonThreadSafe() used to implcitly check in its destructor
   ~Sequence/ThreadChecker() doesn't by design. To keep this CL a
   no-op, an explicit check was added to the destructor of migrated
   classes.
 * NonThreadSafe used to provide access to subclasses, as such
   the |sequence_checker_| member was made protected rather than
   private where necessary.

BUG=676387
This CL was uploaded by git cl split.

R=jianli@chromium.org

Review-Url: https://codereview.chromium.org/2912823002
Cr-Commit-Position: refs/heads/master@{#476415}

storage/browser/blob/shareable_file_reference.cc

@@ -9,15 +9,15 @@
 
 #include "base/lazy_instance.h"
 #include "base/macros.h"
+#include "base/sequence_checker.h"
 #include "base/task_runner.h"
-#include "base/threading/non_thread_safe.h"
 
 namespace storage {
 
 namespace {
 
-// A shareable file map with enforcement of thread checker.
-class ShareableFileMap : public base::NonThreadSafe {
+// A shareable file map with enforcement of sequence checker.
+class ShareableFileMap {
  public:
   typedef std::map<base::FilePath, ShareableFileReference*> FileMap;
   typedef FileMap::iterator iterator;
@@ -26,32 +26,39 @@ class ShareableFileMap : public base::NonThreadSafe {
 
   ShareableFileMap() {}
 
-  ~ShareableFileMap() {
-    DetachFromThread();
-  }
+  ~ShareableFileMap() = default;
 
   iterator Find(key_type key) {
-    DCHECK(CalledOnValidThread());
+    DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
     return file_map_.find(key);
   }
 
   iterator End() {
-    DCHECK(CalledOnValidThread());
+    DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
     return file_map_.end();
   }
 
   std::pair<iterator, bool> Insert(value_type value) {
-    DCHECK(CalledOnValidThread());
+    DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
     return file_map_.insert(value);
   }
 
   void Erase(key_type key) {
-    DCHECK(CalledOnValidThread());
+    DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
     file_map_.erase(key);
   }
 
+#if DCHECK_IS_ON()
+  void AssertCalledOnValidSequence() const {
+    DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+  }
+#endif  // DCHECK_IS_ON()
+
  private:
   FileMap file_map_;
+
+  SEQUENCE_CHECKER(sequence_checker_);
+
   DISALLOW_COPY_AND_ASSIGN(ShareableFileMap);
 };
 
@@ -102,7 +109,9 @@ scoped_refptr<ShareableFileReference> ShareableFileReference::GetOrCreate(
 
 void ShareableFileReference::AddFinalReleaseCallback(
     const FinalReleaseCallback& callback) {
-  DCHECK(g_file_map.Get().CalledOnValidThread());
+#if DCHECK_IS_ON()
+  g_file_map.Get().AssertCalledOnValidSequence();
+#endif  // DCHECK_IS_ON()
   scoped_file_.AddScopeOutCallback(callback, NULL);
 }